Resistor



Sept. 4, 1928.

H. R. VAN DEVENT RESISTOR Filed Nov. 1925 m Patented 4,1928.

van m'ivimm or r iiw roams. 2., nss1emi0n 'ro mama cony nusaa ioonromrzoxpa conrom'non or DELAWARE.

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PATENT, OFFICE.

Original muse"; fled member i-,,1e22,sr1a1iio..604,365. Divided and an application filed This ap lication is a division of my application Sena], No. 604,395, filed December 1, 1922. I I

My invention relates ,to. variable resistl ances, such as variable grid leaks commonl employed in radio telephone and telegrap ap aratus.

ne of the ob'ects of my invention is to rovide an electrical resistance in which rubs ing and scraping or friction of the parts is eliminated.

" Another object of my invention is to rovide a variable electrical resistance in w ich the resistance may be varied by infimtesimal strips.

A further object of my invention is to provide a variable electrical resistance of sturdy construction, which is easily and cheaply made and in which the necessity for repair or replacement is minimized."

. 'Other objects will hereinafter more fully appnear. the drawings: 0

Figure 1 is a view in perspective of a va- 95 riable grid leak resistance; a

Fig. 2-is a perspective view of another form'- of resistance;

Fig. 3 isa perspective view of another modification of the forms shown in Figs. 1

80 and 2. 1 i

Like figures of reference denote the same parts wherever they'are shown.

Referring to the drawings, the device here shown com risesa support or base 1, carry- 85 ing a fixed member 2 forming a resistance 7 element. This said fixed member in the case of a variable grid leak, may be of paper or cardboard, coated with india ink or havin thereon a suitable conducting medium, suc

as a coating of black lead. In some cases the base 1 may have a streak of resistance mate- :rial across its top, in a well known manner.

The member 2 is clamped at one end under the binding post 7 the conducting surface of 2 being in electrical connection therewith. The remainin end of 2 is clamped under and inelectrical connection with binding post 8, therefore, an electrical circuit exists across the strip 2 from 7 to 8. .Glamped under the bindin post7 and in electrical connection therewit is the mem- Iovember 1, 1928.

Serial No. 672,161.

threaded shaft 4, which passes freely througlh the collar; 11, entering a tappedhole knob or handle 6. I The collar 11 is secured to the handle 6 but turns freely in the plate 1. The tapped hole in the handle 6 is long enough to permit the shaft 4.- to enter 6 for a suflicient distance to operate the device as hereinafter described.

, Fig. 2 shows a' modification of the device wherein the movable spring member 3 is positioned at the center of the member 2. Figure 3 is a further modification in which the base member has an upwardly projecting portion 10 rovided with a curved contact surface indicated at 12.

. In operation referring to the form of device shown in Fig. 1 (the same being connected in the circuit for which it is intended, the connection being made to binding posts 7 and 8) by turning the knob or handle 6, the member 3 will be gradually drawn down on the surface of the member 2.

As the member 3 may be of bronze or some other good conducting material, as it gradually lies down upon 2, the resistance of 2 is gradually decreasedby reason of a portion .of 2 becoming short-circuited.

This drawing or lying down action will begin at the point 13 and progress toward the ri ht of the member 2 until the lower side 0 the member 3 is in contact, with the extreme right hand end of the strip 2 such ,as at the point 14. It will be observed that the resistance of the member2 may be varied by very small steps (in fact, imperceptibly) from a maximum to a minimum by operating the knob or handle 6 to draw the strip 3 gradually into contact with 2 whereby the :under surface of 3 is caused to gradually overlay the upper surface of 2 by touch contact.

By touch contact I mean that the members 2 and 3 are caused to approach and recede from each other along a forwardly progressing line substantially perpendicular to inatmg vices ofthis character wherein a movablemember, the

i sliding contactior.

th posed the thereby e1ime P the dificulties heretofore met in de uivalent of 3, is brou htinto 'gement with a resistance mem er, the uivalent of 2, b' means of a rubbmg or 0 like. Such rubbing or sliding contacts are very detrimental in many cases and particularly where a r or cardboard treated with mdia i is employed for the member 2 for in such cases after the movable member has been rubbed along the cardbord surface a iew times, the resistance characteristics of the surface is permanently varied and in many'cases, the member 2 is destroyed. I It has been found in practice that by reason of the fact that the flexible metalllc ele- Y'ment 3 is sometimes intentioned away from the-resistor 2, and the stri 3 is of considerable length, there may portions of it "between its fixed end and the more remote point of contact of the stri 3 with' the surace of the resistor in ,w 'ch the strip 3 will buckle awayfrom closecontact with the resistor surface. This-does not in any manner afl'ectthe operation of the device,

because there is nevertheless a short circuit between the-point -of-fixed contact of the firing 3 with the resistor surface 2 and its timate point'of. contact withsuch resistor Whereverthe member 2 is made in the form of a coiled resistance wire, and the equivalent-ofthe member 3 is moved over the surface-of the-coils in contact with the convolutions thereof, it is obvious that the resistance cannot be varied to a lesser degree than the resistance of a single convolution of the coil, whereas with my device, the resist- 'ance maybe varied by infinitesimal steps depending uponthe. itchof the thread of the member 4 and the egree of movement given to knob'or handle 6. In'the arrangement'ishown' in resistance of the member 2 is varied drawing the member 3.,against 2.= The screw 4 is provided with ahead 4- that bearsthrough =a washer9' on a plate 9. .The pre'ssure of the plate 9 flexes the curved s 3. In'the midway operated position,*-t e member 3 occupies the position shown in-the dotted lines ance of the circuit between the -7 and 8 willbe reduced.

of Fig.2. .The member 3 being of metal and a good conductor as compared with the member2 which may have a surface of com-' parativeli high resistance, a .portion -of' 2 will be ort-circuited, whereby ;the.resist- The modification shown in Fig. 3

- in providing the fixed inemberj2'. with anupr 'curved or otherwise formed surface. e operation of this device'is-f'substantially 'e ement to va '4. An electrical device comprising a base, a fixed impedance element. thereon, .a resil- 2, the

binding posts the same as the device shown grid leak, it is obvious t at it may be employed forother uses and that any device avingmembers so arranged that one member is used to short circuit the other by touch rather than sliding contact;i will come within the scope of the appen 'Iclaim:-

1. An electrical resistance comprising a.

ed claims.

in the precedin figures. 01$ Vh1le for the sake ofillustration I have shown the invention as aglplied to a variable fixed resistance element, a resilient movable I element, a threaded member havin grooves to engage the movable element, an a screw for moving the threaded member to cause the movable element to be progressively moved towardand away from the fixed element to vary the resistance of the device.

2. An electrical device comprising abase,

a fixed'resistance element thereon, a resilient movable element fastened at one .end above the fixed element,and havingthe other end bifurcated, a nut having grooved sides. to

receive such bifurcations, and a screw for.

moving the nut to cause the movable element to be progressively moved toward and away from the'fixed element to vary theresistance flexible element of greatenconductivity than the first normally-in contact at one end with said first element, but divergent with respect to the first element awa from said end the 1 moved toward and away from 1 the resistance of the device.

.divergent end being bi rcated, a nut. av-

ing grooved. sides to receive such bifurcations, and a screw for moving the nutto cause the movable element to be pro Ill ient, movable conducting element fastened at a-predetermined point'to thejfixed element 1 butnormally divergent with respect .to said fixed element away from said pomt', the conducting element havingm portion removed at an end awaye fromthe predetermined point,

a member having grooves which en ge the conductingelement at the place'w ereithe said portion was removed, and a meansffor mov' the grooved member in such manner that the movable conducting. elegient mag obs an away 111 progressively moved towar theildevice. h f I fix testimon .w ereo a m" ature.

the fixed element to vary the impedance of 

